Use GetSyntheticArrayMember to subscript pointers and out of bounds index from arrays

Author: kuilpd

lldb/include/lldb/ValueObject/DILEval.h

@@ -55,8 +55,6 @@ class Interpreter : Visitor {
   llvm::Expected<lldb::ValueObjectSP>
   Visit(const ArraySubscriptNode *node) override;
 
-  lldb::ValueObjectSP PointerAdd(lldb::ValueObjectSP lhs, int64_t offset);
-
   // Used by the interpreter to create objects, perform casts, etc.
   lldb::TargetSP m_target;
   llvm::StringRef m_expr;

lldb/source/ValueObject/DILEval.cpp

@@ -18,22 +18,6 @@
 
 namespace lldb_private::dil {
 
-static lldb::ValueObjectSP
-ArrayToPointerConversion(lldb::ValueObjectSP valobj,
-                         std::shared_ptr<ExecutionContextScope> ctx) {
-  assert(valobj->IsArrayType() &&
-         "an argument to array-to-pointer conversion must be an array");
-
-  uint64_t addr = valobj->GetLoadAddress();
-  llvm::StringRef name = "result";
-  ExecutionContext exe_ctx;
-  ctx->CalculateExecutionContext(exe_ctx);
-  return ValueObject::CreateValueObjectFromAddress(
-      name, addr, exe_ctx,
-      valobj->GetCompilerType().GetArrayElementType(ctx.get()).GetPointerType(),
-      /* do_deref */ false);
-}
-
 static lldb::ValueObjectSP LookupStaticIdentifier(
     VariableList &variable_list, std::shared_ptr<StackFrame> exe_scope,
     llvm::StringRef name_ref, llvm::StringRef unqualified_name) {
@@ -327,21 +311,6 @@ Interpreter::Visit(const UnaryOpNode *node) {
       m_expr, "invalid ast: unexpected binary operator", node->GetLocation());
 }
 
-lldb::ValueObjectSP Interpreter::PointerAdd(lldb::ValueObjectSP lhs,
-                                            int64_t offset) {
-  uint64_t byte_size = 0;
-  if (auto temp = lhs->GetCompilerType().GetPointeeType().GetByteSize(
-          lhs->GetTargetSP().get()))
-    byte_size = *temp;
-  uintptr_t addr = lhs->GetValueAsUnsigned(0) + offset * byte_size;
-
-  llvm::StringRef name = "result";
-  ExecutionContext exe_ctx(m_target.get(), false);
-  return ValueObject::CreateValueObjectFromAddress(name, addr, exe_ctx,
-                                                   lhs->GetCompilerType(),
-                                                   /* do_deref */ false);
-}
-
 llvm::Expected<lldb::ValueObjectSP>
 Interpreter::Visit(const ArraySubscriptNode *node) {
   auto lhs_or_err = Evaluate(node->lhs());
@@ -373,22 +342,21 @@ Interpreter::Visit(const ArraySubscriptNode *node) {
         m_expr, "array subscript is not an integer", node->GetLocation());
 
   // Check to see if 'base' has a synthetic value; if so, try using that.
+  uint64_t child_idx = index->GetValueAsUnsigned(0);
   if (base->HasSyntheticValue()) {
     lldb::ValueObjectSP synthetic = base->GetSyntheticValue();
     if (synthetic && synthetic != base) {
       uint32_t num_children = synthetic->GetNumChildrenIgnoringErrors();
       // Verify that the 'index' is not out-of-range for the declared type.
-      if (index->GetValueAsSigned(0) >= num_children) {
-        auto message =
-            llvm::formatv("array index {0} is not valid for \"({1}) {2}\"",
-                          index->GetValueAsSigned(0),
-                          base->GetTypeName().AsCString("<invalid type>"),
-                          base->GetName().AsCString());
+      if (child_idx >= num_children) {
+        auto message = llvm::formatv(
+            "array index {0} is not valid for \"({1}) {2}\"", child_idx,
+            base->GetTypeName().AsCString("<invalid type>"),
+            base->GetName().AsCString());
         return llvm::make_error<DILDiagnosticError>(m_expr, message,
                                                     node->GetLocation());
       }
 
-      uint64_t child_idx = index->GetValueAsUnsigned(0);
       if (static_cast<uint32_t>(child_idx) <
           synthetic->GetNumChildrenIgnoringErrors()) {
         lldb::ValueObjectSP child_valobj_sp =
@@ -410,25 +378,14 @@ Interpreter::Visit(const ArraySubscriptNode *node) {
         m_expr, "subscript of pointer to incomplete type 'void'",
         node->GetLocation());
 
-  if (base_type.IsArrayType())
-    base = ArrayToPointerConversion(base, m_exe_ctx_scope);
-
-  CompilerType item_type = base->GetCompilerType().GetPointeeType();
-  lldb::addr_t base_addr = base->GetValueAsUnsigned(0);
-
-  llvm::StringRef name = "result";
-  ExecutionContext exe_ctx(m_target.get(), false);
-  // Create a pointer and add the index, i.e. "base + index".
-  lldb::ValueObjectSP value =
-      PointerAdd(ValueObject::CreateValueObjectFromAddress(
-                     name, base_addr, exe_ctx, item_type.GetPointerType(),
-                     /*do_deref=*/false),
-                 index->GetValueAsSigned(0));
-
-  lldb::ValueObjectSP val2 = value->Dereference(error);
-  if (error.Fail())
-    return error.ToError();
-  return val2;
+  if (base_type.IsArrayType()) {
+    uint32_t num_children = base->GetNumChildrenIgnoringErrors();
+    if (child_idx < num_children)
+      return base->GetChildAtIndex(child_idx);
+  }
+
+  int64_t signed_child_idx = index->GetValueAsSigned(0);
+  return base->GetSyntheticArrayMember(signed_child_idx, true);
 }
 
 } // namespace lldb_private::dil